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I don't know of any CPU that speculates both sides of a branch. I work on a CPU design team.

Modern CPUs speculate hundreds of instructions ahead, and with just a dozen branches you can have a few thousand different paths. It makes more sense to speculate down one path with very high accuracy.

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This is the right answer. :)

I think a lot of folks get mixed up with GPU and/or SIMD architecture, where you execute both sides of the branch out of necessity: Some of the lanes need to go one way and some the other, so you have to do both.

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